Conventionally, there is a resolver disclosed in Japanese Patent No. 4,783,752, for example, as a rotational angle detecting device provided with a correction circuit for correcting detection results.
The resolver includes a PROM, a correction coefficient calculating section, and a correcting section.
Here, the PROM, the correction coefficient calculating section, and the correcting section correspond to the correction circuit.
The resolver is a device that detects a rotational angle of a rotational shaft of a motor.
The resolver is mounted on the rotational shaft of the motor.
Meanwhile, when a current flows through the motor, there may be a magnetic flux leaking from the rotational shaft.
As a result, the leaked magnetic flux is applied to the resolver as a disturbance magnetic flux, and the detection result of the resolver may be changed.
In other words, a rotational angle error occurs.
In order to correct the rotational angle error, data indicating a relationship between the disturbance magnetic flux and the rotational angle error is stored in the PROM.
Specifically, data indicating a relationship between the current flowing through the motor and the rotational angle error is stored in the PROM.
The correction coefficient calculating section calculates a correction factor based on the data stored in the PROM and the detected current flowing through the motor.
The correcting section corrects the detection result of the resolver based on the correction coefficient that the correction coefficient calculating section has calculated, and outputs a rotational angle of the rotational shaft.
Thus, it is possible to suppress a rotational angle error caused by the disturbance magnetic flux being applied from occurring.
Incidentally, in the resolver described above, in order to correct the rotational angle error, it is necessary to store the data representing the relationship between the current flowing through the motor and the rotational angle error.
The current flowing through the motor variously changes in a predetermined current region.
Therefore, the data representing the relationship between the current flowing in the motor and the rotational angle error must be stored for all of the current in the current region.
In other words, the data indicating a relationship between the disturbance magnetic flux and the rotational angle error applied to the resolver for all the disturbance magnetic flux in disturbance magnetic flux regions that may be applied must be stored.
Therefore, volume of data to be stored becomes enormous. As a result, an enormous storage region is required. In addition, it takes time and effort to prepare data.